Motor powered vehicles for hauling loads or pulling farm implements have been in use for a long period of time, but have recently kindled an interest in individual competition indicative of the power of a particular vehicle. So called tractor pulling contests have become popular and have led to the development of apparatus that acts to produce an increasingly greater resistance to the pull of the tractor until it is substantially slowed down, or actually stopped.
Prior art has commonly used large flat ground engaging sleds with increasingly added weight. More recently self-contained apparatus has been developed to accomplish this task. Along with interest in this type of competition, model builders have also been active in developing miniature vehicles powered by electricity or liquid fuel that simulate an actual tractor, truck or automobile. They too have created a need for measuring apparatus on a small scale that duplicates the function of the test sled. While the performance parameters are of the same nature, other problems arise not solved by prior art using a miniature replica.
The following U.S. patents are considered related to the invention:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 3,659,455 Watkins 2 May 1972 3,491,590 Watkins 27 January 1970 1,603,521 Davidson 19 October 1926 ______________________________________
Watkins in his first patent discloses a full-size weight transfer apparatus utilizing a sled upon which a tractor is statically positioned for dead weight and a cable is staked into the ground with a pulley arrangement providing movement of dead weight progressively over center. Further, an automatic trolley release mechanism is used that is responsive to movement of the apparatus at the end of the pull.
In Watkins second patent, an additional improvement is disclosed wherein a truck chassis is utilized for the dead weight and a sled is attached underneath with a fifth wheel, the front wheels of the chassis resting thereupon. The skid is removable allowing the truck, as the self-propelling means, to tow the skid to the starting point. Also, this disclosure employs a power take off from the prime mover to linearly move a dead weight on the chassis.
Davidson discloses a dynometer having a pair of skids 13 with a weighted container 17 on a pair of sloping guide rails with wheels 11 on the rear portion. In operation the tractive power is attached to a cable 19 that slides the container up the angular rails, decreasing the weight on the skids as more power is exerted. This structure and function is in direct opposition to the instant invention.
For background purposes and as indicative of the art to which the invention relates reference may be made to the following additional U.S. patents:
______________________________________ 2,768,823 Lindars 30 October 1956 2,622,868 Yeasting 23 December 1952 2,518,568 Pease 15 August 1950 2,392,023 Cooper 1 January 1946 ______________________________________